废水磷回收产物在土壤重金属钝化中高效利用的基础研究

Phosphorus is an essential element for all life forms and is predicted to be depleted in the next 70 years in China. Although struvite crystallization has been intensively investigated as an effective green technology for efficient phosphorous recovery, there are currently few industrial applications due to the fact that the price of recovered struvite is higher than traditional fertilizer. Therefore, add value to recovered struvite is of great significance. It is well known that the proper phosphate addition to heavy metal contaminated soil is effective for soil remediation. As a source of phosphate, struvite and other products recovered from wastewater might also be a good material for soil remediation, where the release of phosphorus promotes the formation of metal-phosphate. Therefore, the current research proposes to used recovered phosphate products from wastewater for contaminated soil remediation, where the reaction mechanisms, influencing factor and heavy metal leaching and dissolving behaviours will be examined. An amended phosphate product for heavy metal immobilization will then be designed to further reduce the cost. By doing this, a ‘bridge’ between wastewater treatment and soil remediation could be constructed, where the remediation of contaminated soil could also promote the commercialization of current phosphorus recovery technologies to reduce the phosphorus footprint in the country.

磷是食品生产必需的元素，是生命不可替代的组分，也是不可自然再生的有限资源。然而，我国现在的磷矿储量仅够维持使用70年左右。虽然磷酸铵镁作为一种高效的磷回收技术受到了广泛关注，但由于其与传统肥料相比并不具备价格优势，扩大其应用场景，提高产品附加值成为该领域的研究瓶颈。本研究以废水回收的磷酸铵镁为基础，探讨废水磷回收产物(磷酸铵镁，磷酸钾镁，羟基磷灰石)作为土壤重金属钝化剂的可行性，对比其稳定化效果，并揭示钝化及溶解过程的影响因素和反应机理。在此基础上，找到一种基于废水磷回收产物的高效复合土壤钝化剂，从而改变磷酸铵镁的应用场景，在进行土壤重金属污染修复的同时促进了废水磷回收技术的推广应用。

磷酸铵镁结晶矿化是磷资源高效循环利用和水环境持续稳定提升的重要保障技术。但其回收产物较低的肥料价值限制了其推广应用。本项目旨在探索不同废水磷回收产物(磷酸铵镁、磷酸钾镁、羟基磷灰石)作为土壤重金属钝化剂的技术可行性，阐释不同磷回收产物的稳定化效果、反应机理和重金属扩散过程。项目阐明了废水重金属与不同磷回收产物作用的竞争机制和选择性调控规律，量化了磷酸铵镁结晶过程中有机物对重金属形态分布的影响，明确了铜和锌在磷酸铵镁结晶过程中的作用机制，研发了磷回收过程中的重金属减量化控制工艺。在此基础上，通过室内和原位实验，辨析了磷酸铵镁、磷酸钾镁、羟基磷灰石三种磷酸盐修复剂对壤pH、Pb和Cd化学形态分布、土壤酶活性以及土壤微生物多样性的影响，阐明了磷回收产物在土壤重金属钝化过程中的反应和扩散机理，为土壤重金属污染的修复提供了理论基础。项目执行期间，进行了磷回收过程中重金属减量化控制中试实验，可以减少回收的产物中43.5％的铜和77.6％的锌。此外，项目执行期间发表期刊论文6 篇，参加学术会议 1 次，申请发明专利 1项，培养硕士研究生1人，本科生4名。项目成果在进行土壤重金属污染修复的同时促进了废水磷回收技术的推广应用，为污水磷回收产物的高度附加值利用和重金属污染土壤的可持续高效修复提供了技术支撑。